JP2008151925A - Fixing discharge device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus having a recorded material discharge section causing no nonuniform gloss without marking a roller on a recorded material after fixing. <P>SOLUTION: A fixing shaft for each of rollers for a fixing discharge section is made of PTC. A ring made of a highly releasable resin such as PFA is attached to the periphery of the roller, to be used as the roller for the fixing discharge section. By supplying the power of the PTC, the ring used as the roller for the discharge section can be heated. By selecting PTC to maintain a temperature at which nonuiform gloss caused by the roller mark hardly occurs, equilibrium is kept at a fixed temperature with no control. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an apparatus having a fixing device that heats and fixes a toner image formed and supported on a recording material. The recording material on which the toner image is fixed by heating is sandwiched by a pair of rotating means. The present invention relates to a recording material discharging apparatus that discharges a recording material by rotating a pair of rotating means, and an image forming apparatus such as a copying machine and a printer including the recording material discharging apparatus.

  For example, in an image forming apparatus such as an electrophotographic process or an electrostatic recording process, an unfixed image formed and supported on a recording material (transfer paper, printing paper, photosensitive paper, electrostatic recording paper, etc.) by a transfer method or a direct method. As a heat fixing device for heat fixing a toner image, devices of various methods and configurations such as a heat roller method, a film heating method, and an electromagnetic induction heating method are known.

In a device having a fixing device that heats and fixes a toner image formed and carried on a recording material, the recording material on which the toner image is fixed by heating is sandwiched by a pair of rotating means, and the pair of rotations As a recording material discharge device for discharging a recording material by rotating the means, and an image forming apparatus such as a copying machine and a printer equipped with this recording material discharge device, in Patent Document 1, FIG. As shown in the pair of transport rollers 41, the configuration is such that the transport roller 44 on the toner surface side immediately after fixing is used as a through roller so that the rollers are in uniform contact with the toner surface. Yes.
Japanese Patent Laid-Open No. 2003-238003

  However, according to the above-described conventional technique, the conveyance roller 44 is a through roller, but the other conveyance roller 45 for nipping and conveying the recording material is not through, so that the recording material that has not been sufficiently cooled immediately after fixing is used. Since the toner image surface of the recording material is cooled more quickly than the non-clamping portion by contacting the conveyance roller 45 from the back side of the toner image surface, the roller traces are unevenly glossy on the toner image surface of the recording material. Will occur. Further, if the conveying roller 45 is a passing roller in the same manner as the conveying roller 44, there is no escape space for the vapor generated by overheating the recording material, and it accumulates in the nip of the conveying roller and causes an image defect.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-described problems in the prior art and provide an image forming apparatus provided with a recording material discharge portion that does not leave a roller mark on a recording material after fixing and does not cause gloss unevenness. And

  In order to achieve the above object, the present invention provides a method in which a recording material on which an unfixed toner image is formed is nipped and conveyed, and the unfixed image is heated and fixed on the recording material as a permanent image by a heat fixing device, and then heated and fixed. In a pair of discharge rollers composed of a drive discharge roller for discharging from the apparatus and a driven discharge roller opposite to the drive discharge roller, the driven discharge roller forms a heating element or a heat generating portion holding the heating element, and the fixed shaft Has a cylindrical roller that is rotatably fitted, and the cylindrical roller is opposed to the drive discharge roller and is driven and nipped and conveyed by the heated fixing device to be recorded and discharged from the fixing heating device. It is characterized by doing.

  As described above, according to the present invention, the fixed shaft itself of the driven discharge roller forms a heating element or a heat generating portion holding the heating element, and a cylindrical roller that is rotatably fitted to the fixed shaft is provided. By having the cylindrical roller fitted by the fixed shaft of the driven discharge roller before the recording material on which the toner image has been fixed in the heat fixing unit is sandwiched between the drive discharge roller and the driven discharge roller. It becomes possible to heat and heat the clamping part on the opposite side of the drive discharge roller. The recording material is heated to around 200 ° C. in the heat fixing part and has a temperature of around 140 ° C. even immediately after the fixing process. However, by increasing the temperature of the sandwiching part of the discharge roller pair in advance, the recording material is The temperature difference between the recording material and the nipping portion is reduced when nipped by the discharge roller pair, and the portion nipped by the discharge roller pair is reduced from becoming a roller trace as gloss unevenness on the toner image surface of the recording material. It is possible.

(Example 1)
FIG. 1 shows the configuration of the first embodiment, and is a diagram that best represents the characteristics of the present invention. An example showing the configuration of the image forming apparatus including the heating device of this embodiment is shown in FIG. The image forming apparatus of this example is a laser beam printer using a transfer type electrophotographic process.

  FIG. 5 is a cross-sectional view of a tandem type color LBP (color laser printer) as an example of the image forming apparatus according to the present invention.

  In FIG. 5, reference numeral 1 (1a to 1d) denotes a drum-type electrophotographic photosensitive member (hereinafter referred to as a photosensitive drum) as a latent image carrier that rotates in a direction indicated by an arrow (counterclockwise) at a predetermined process speed. The photosensitive drums 1a, 1b, 1c, and 1d respectively share a yellow (Y) component, a magenta (M) component, a cyan (C) component, and a black (Bk) component of a color image. These photosensitive drums 1a to 1d are rotationally driven by a drum motor (DC servo motor) (not shown), but independent driving sources may be provided for the respective photosensitive drums 1a to 1d. The rotational drive of the drum motor is controlled by a DSP (digital signal processor) (not shown), and other controls are performed by a CPU (not shown).

  Further, the electrostatic adsorption conveyance belt 9a is stretched around a driving roller 9b and a driven roller 9c, and is driven to rotate in the direction indicated by the arrow by the driving roller 9b to adsorb and convey the recording medium S.

  Hereinafter, yellow (Y) of the four colors will be described as an example.

  The photosensitive drum 1a is uniformly charged to a predetermined polarity and potential by the primary charging means 2a during the rotation process. The photosensitive drum 1a is exposed to a light image by a laser beam exposure means (hereinafter referred to as a scanner) 3a, and an electrostatic latent image of image information is formed on the photosensitive drum 1a.

  Next, a toner image is formed on the photosensitive drum 1a by the developing unit 4a, and the electrostatic latent image is visualized. Similar steps are performed for the other three colors (magenta (B), cyan (C), and black (Bk)).

  Thus, the four color toner images are synchronized with the photosensitive drums 1a to 1d by the registration rollers 10b that stop and re-transport the recording medium S conveyed by the paper feed roller 10a at a predetermined timing. The toner images are sequentially transferred onto the recording medium S at the nip portion with the belt 9a. At the same time, the photosensitive drums 1a to 1d after the transfer of the toner image to the recording medium S are subjected to repeated image formation by removing residual deposits such as transfer residual toner by the cleaning means 6a, 6b, 6c and 6d. .

  The recording medium S on which the toner images are transferred from the four photosensitive drums 1a to 1d is separated from the surface of the electrostatic attraction / conveying belt 9a at the driving roller 9b and sent to the fixing device 5, where the pressure roller 5a and the heating rotator are provided. The toner image is fixed on the recording medium S while being nipped and conveyed at 5 b, and is nipped and conveyed by the drive discharge roller 7 and the driven discharge roller 8 and is discharged to the discharge tray 13.

  FIG. 1 shows the configuration of the drive discharge roller 7 and the driven discharge roller 8 of this embodiment. FIG. 2 shows details of the driven discharge roller 8.

The drive discharge roller 7 receives a rotational force at the end of the shaft 7a from a drive means well (not shown), and rotates a plurality of rollers 7b formed of silicon rubber or the like fixed on the shaft 7a. The driven discharge roller 8 includes a fixed shaft 8b formed of PTC, a cylindrical roller 8a rotatably fitted on the fixed shaft 8b, a holder 8c for holding the fixed shaft 8b, and a roller of the cylindrical discharge roller 7 that drives the cylindrical roller 8a. A spring 8d for applying pressure to 7b and a contact portion 8e for supplying electric power to a fixed shaft 8b formed of PTC are configured. PTC is an oxide semiconductor based on barium titanate based on barium titanate (BaTiO ₃ ) and added with a small amount of rare earth elements to make it conductive. It can be processed into an arbitrary shape. The contact portion 8e is directly soldered to the PTC and coated with a heat resistant paint or the like for electrical insulation and mechanical protection. The PTC that forms the fixed shaft 8b is used for the purpose of heating, and as a heating element whose temperature rises quickly due to the initial current at the time of voltage application, the property of compensating the heat generation according to the thermal load is used. Thus, by selecting a PTC having a characteristic that maintains equilibrium at a preset temperature, it becomes possible to maintain a constant temperature without control. It can be used as a simple heating element that does not require a temperature control circuit such as a bimetal. In addition, it is possible to control the power supply to the PTC in accordance with the type of the recording material S and the temperature control temperature of the heating rotator 5b. It is also possible to control the power supply to the PTC. At this time, the temperature setting of the PTC varies depending on the configuration, but is approximately 140 ° C. The cylindrical roller 8a is formed of a resin having both heat resistance and non-adhesiveness such as PFA and PTFE, and is difficult to adhere toner or paper dust to the surface. As shown in FIG. 2, the fixed shaft 8b has a D-cut surface 8b ′ for fixing to a holder 8c made of heat-resistant resin. The driven discharge roller 8 is pressed against the roller 7b by the pressure spring 8d, and is rotated by the rotation of the drive discharge roller 7, so that the toner image is fixed while being nipped and conveyed by the pressure roller 5a and the heating rotator 5b. The recorded recording medium S is nipped and conveyed and discharged to the discharge tray 13.

  As described above, the fixed shaft itself of the driven discharge roller is a heating element, and the fixed shaft has a cylindrical roller that is rotatably fitted, so that the fixing process of the toner image is performed in the heat fixing unit. Before the recording material is sandwiched between the drive discharge roller and the driven discharge roller, the cylindrical roller fitted by the fixed shaft of the driven discharge roller is heated, and the clamping portion on the opposite drive discharge roller side is heated. Is possible. The recording material is heated to around 200 ° C in the heat fixing part and has a temperature of around 140 ° C even immediately after the fixing process, but the temperature of the clamping part of the discharge roller pair is raised to around 140 ° C in advance according to the configuration. Therefore, when the recording material is sandwiched by the discharge roller pair, the temperature difference between the recording material and the sandwiching portion is reduced, and the portion sandwiched by the discharge roller pair becomes uneven gloss on the toner image surface of the recording material. It is possible to reduce the occurrence of roller marks. At this time, because the fixed shaft is formed of PTC, the fixed shaft itself is a resistance heating element, and by supplying power, it is possible to keep the equilibrium state uncontrolled at a temperature determined by the preset PTC characteristics. Therefore, gloss unevenness due to roller marks is reduced by controlling the power supply to the PTC according to the combination of the recording material that tends to cause roller marks as gloss unevenness on the toner image surface and the temperature control temperature during fixing. Such optimization can be achieved. Further, by controlling the power supply to the PTC in one recording material in the nipping conveyance by the pair of discharge rollers, it is possible to optimize the gloss unevenness due to the roller marks in the page.

(Example 2)
A second embodiment is shown in FIG.

  Since the configuration of the image forming apparatus including the fixing and discharging apparatus of the present embodiment is the same as that described with reference to FIG. This embodiment corresponds to the driven discharge roller 8 in 5, and the details will be described with reference to FIG. Hereinafter, the same members as those in FIGS. 1 and 2 having the same function are denoted by the same reference numerals and the description thereof is omitted.

  FIG. 3 is a cross-sectional view of the center of the cylindrical portion of the driven discharge roller 8. The central portion is a fixed shaft 8b formed of PTC, and a circular ring made of metal such as aluminum or SUS on the outer periphery thereof. A release layer 11b made of a fluororesin is formed on the surface of the ring 11a facing the drive discharge roller 7 by means such as coating or tube clothing.

  As described above, by using a metal having a high thermal conductivity for the cylindrical roller, the heating time can be shortened, and by providing a release layer of the fluororesin, the roller surface can have non-adhesiveness, When the roller contacts the toner image surface of the recording material, it becomes possible to reduce the transfer of the toner image to the roller, and to the recording material by the maximum transfer of the toner image from the roller to the recording material. Dirt can be reduced.

(Example 3)
A third embodiment is shown in FIG.

  Since the configuration of the image forming apparatus including the fixing and discharging apparatus of the present embodiment is the same as that described with reference to FIG. This embodiment corresponds to the driven discharge roller 8 in FIG. 5, and details thereof will be described with reference to FIG. Hereinafter, the same members as those in FIGS. 1 and 2 having the same function are denoted by the same reference numerals and the description thereof is omitted.

  FIG. 4 shows the driven discharge roller 8. In the figure, there is a through hole for holding the resistor 13 at the center of the fixed shaft 12, the resistor 13 is held inside, and a cylindrical roller 8a is provided on the outer periphery thereof. The fixed shaft 12 is formed of a thin heat-resistant resin or a metal whose surface is insulated, and has D-cut surfaces 12 'for fixing to the holder 8c at both ends thereof.

  As described above, by configuring the fixed shaft from the resistor and the resistance holding member that fixes and holds the fixed shaft, the cylindrical roller can be heated with the fixed shaft as a resistance heating element in an easy form. The effect of heating the cylindrical roller is the same as that of the first invention. When the recording material is sandwiched between the discharge roller pair, the temperature difference between the recording material and the sandwiching portion is reduced, and the recording roller is sandwiched between the discharge roller pair. It is possible to reduce that the portion becomes a roller trace as uneven gloss on the toner image surface of the recording material.

FIG. 3 is a diagram illustrating a discharge roller pair according to the first embodiment of the present invention. FIG. 3 is a diagram illustrating a driven discharge roller according to the first embodiment of the present invention. FIG. 5 is a view showing a cross section of a driven discharge roller according to a second embodiment of the present invention. FIG. 6 is a diagram for explaining a driven discharge roller according to a third embodiment of the present invention. FIG. 4 is a diagram illustrating image forming apparatuses according to first to third embodiments of the present invention.

Explanation of symbols

1 Photosensitive drum 2 Primary charging means 3 Laser beam exposure means (scanner)
DESCRIPTION OF SYMBOLS 4 Development part 5 Fixing device 5a Pressure roller 5b Heating rotary body 6 Cleaning means 7 Drive discharge roller 8 Driven discharge roller 8a Cylindrical roller 8b Fixed shaft 8c Holder 8d Spring 8e Contact part 9a Electrostatic adsorption conveyance belt 9b Drive roller
10a Paper feed roller
10b Registration roller
11a ring
11b Release layer
12 Fixed shaft
12 'D-cut surface
13 Resistance

Claims (5)

A drive discharge roller for nipping and conveying a recording material on which an unfixed toner image is formed, and fixing the unfixed image as a permanent image on the recording material by a heat fixing device, and then discharging it from the heat fixing device And a pair of discharge rollers composed of a driven discharge roller opposite to it,
The driven discharge roller has a fixed shaft itself forming a heating element or a heat generating portion holding the heating element, and has a cylindrical roller rotatably fitted to the fixed shaft. A fixing discharge device characterized in that the recording material heat-fixed by the heat-fixing device is nipped and conveyed while being opposed to a discharge roller and discharged from the fixing-heating device.   2. The fixing discharge device according to claim 1, wherein the fixed shaft of the driven discharge roller is formed of a PTC thermistor, and the cylindrical roller is rotatably fitted to the fixed shaft and fixedly held. And a contact for applying a voltage to both ends thereof.   2. The fixing discharge device according to claim 1, wherein the fixed shaft of the driven discharge roller includes a resistor and a resistance holding member that fixes and holds the resistor, and the cylindrical roller is rotatably fitted to the fixed shaft. A fixing and discharging apparatus, wherein a cylindrical portion, a fixed holding portion, and contacts for applying a voltage to both ends thereof are arranged.   2. The fixing discharge device according to claim 1, wherein the cylindrical roller of the driven discharge roller is made of a fluorine-based resin and is rotatably fitted to the fixed shaft. Discharging device.   2. The fixing discharge device according to claim 1, wherein the cylindrical roller of the driven discharge roller is formed of a metal cylindrical ring, and a surface of the metal cylindrical ring facing the driving discharge roller is a fluorine-based resin. A fixing discharge device characterized by forming a release layer.

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